Sarcocystosis in man: a report of two cases

Human infections with Sarcocystis species

Recurrent outbreaks of muscular sarcocystosis among tourists visiting islands in Malaysia have focused international attention on sarcocystosis, a disease once considered rare in humans. Sarcocystis species require two hosts, definitive and intermediate, to complete their life cycle. Humans can serve as definitive hosts, with intestinal sarcocystosis for two species acquired from eating undercooked meat: Sarcocystis hominis, from beef, and Sarcocystis suihominis, from pork. Symptoms such as nausea, stomachache, and diarrhea vary widely depending on the number of cysts ingested but appear more severe with pork than with beef. Humans serve as intermediate hosts for Sarcocystis nesbitti, a species with a reptilian definitive host, and possibly other unidentified species, acquired by ingesting sporocysts from feces-contaminated food or water and the environment; infections have an early phase of development in vascular endothelium, with illness that is difficult to diagnose; clinical signs include fever, headache, and myalgia. Subsequent development of intramuscular cysts is characterized by myositis. Presumptive diagnosis based on travel history to tropical regions, elevated serum enzyme levels, and eosinophilia is confirmed by finding sarcocysts in muscle biopsy specimens. There is no vaccine or confirmed effective antiparasitic drug for muscular sarcocystosis, but anti-inflammatory drugs may reduce symptoms. Prevention strategies are also discussed.

Sarcocystis and sarcocystosis in India: status and emerging perspectives

Sarcocystis spp. are a group of tissue cyst-forming coccidia which infect a vast range of animals as well as human beings. Found frequently in animal carcasses at slaughter, undermining their value, they have also been found associated with clinical disease. Dogs and cats are involved in the transmission. Studies in India point to a vast reservoir of infection with high prevalence rates in various livestock species. However, there is a glaring paucity of reports on the horse and Sarcocystis of the camel has remained totally unexplored so far. At least two different Sarcocystis spp. can parasitize each livestock host species. Experimental transmission studies have provided additional parameters for distinguishing the species. The clinical symptoms are generally non-specific and diagnosis in the living animal, by the presently available means, is almost impossible. Immunodiagnosis till now is beset with problem of cross-reactivity. Treatment with anti-coccidials presently tried do not seem satisfactory. Of the two zoonotic species with cattle-man and pig-man cycles, only the latter seems of some significance in India due to backyard pig-rearing and slaughter practices. It is a paradox that despite high prevalence of S. suihominis in pigs, reports of human cases are limited. This and some of the existing grey areas of information in the Indian context, have been highlighted as also possible directions for future research.

Diagnosis of human sarcocystis infection from biopsies of the skeletal muscle

Sarcocystis is an uncommon parasitic infection. We report four cases that presented with lumps, pain in the limbs or a discharging sinus of unknown etiology. Microscopic examination of the excised tissue in all cases showed characteristic cysts of the sarcocystis parasite. A discussion of the identification and recognition of this uncommon infection from muscle biopsies is given.

High prevalence of human skeletal muscle sarcocystosis in south-east Asia

The prevalence of human skeletal muscle sarcocystosis in Malaysia was determined by serial examination of formalin-fixed, paraffin-embedded sections of tongue tissues obtained from consecutive, routine autopsies of subjects aged 12 years or more. Of 100 tongues examined, 21% were found to contain Sarcocystis; 66 cysts were found. The number of cysts per case varied from 1 to 13. In one case, 5 cysts were found in a single tissue section. The age range of positive cases was from 16 to 57 years (mean 37.7 years). Prevalence did not differ with regard to race, sex or occupation. The prevalence of human muscular sarcocystosis in our study was higher than that reported elsewhere. Preferential localization of Sarcocystis in tongue or head and neck and/or genuinely high prevalence in south-east Asia are possible explanations for this observation.

Rapid nucleotide sequence analysis of the small subunit ribosomal RNA of Toxoplasma gondii: evolutionary implications for the Apicomplexa

A method for obtaining a large proportion of the nucleotide sequence of the small subunit ribosomal RNA (srRNA) was applied to the obligate intracellular protozoon Toxoplasma gondii. The method uses reverse transcription of as little as 8 micrograms of total cellular RNA. This fast, efficient method has numerous advantages over traditional gene cloning methods when nucleotide sequences are required for evolutionary studies. A phylogenetic analysis of the srRNA sequence data showed that T. gondii is not especially closely related to any other organism for which srRNA sequences are available, including another member of the Apicomplexa.